Extraction of tin from ores or materials containing tin



Patented Oct. .28, 1930 1.1;EE? smart- PATENT: oFFieE EneAn'AnTHUn.asncn-or'r, or wAY HOUSE, new, Asziiauaron, ENGLAND i -x'rnacrron orTIIN FROM ones on rrarsnmtsconrarnme TIN N oDraw i'ngf Applicationfiledz May 5-, 1928,5eria1 m. 22 5 550, and in Great Britain July731927.

This invention relates to improvements in the metallurgy oftin bearingores or mate rials whereby 'thevaluable contents thereof may be 7extracted in a more convenient and 5 economical.manner'than heretofore.

It is usefulin the treatment ofores, C0111 centrates, slags, 7;all ,0ys,residues or tin containing materials o1" almost any kind Particularly itisiuseful in the extraction offtin from ores or concentrates containingtin in' the for-moi cassiteritejsu'ch as the well known lode tln? orallLl-Vlal? ores which occur throughout' the world, or of any; form of;

concentrates therefrom; w a; '15 The present invention 1s characterlzedin that during or after the reduction ofthe tint bearing -minerals orcompoundsefor instance gcassiterite or tin slag compounds by anysuitable reducmg agent- 1 employ a catalyzing or carrying, salt andanother imetalwhich- I will calla collecting metal and which is.preferably the; metal nickel into which under the conditions stated thetin willflenter and alloy thereWithQleav-ingr the body otvore or ganguematter nearly or Vbysimple screeni'ng,.the other materials hav quitefree from tin. Itis further characterized: by the recovery oi the tinfrom its alloy with the collecting metal in any useful forms I orcombinations and by any of several ape tpropriateme'a ns, all'ashereinafter explained.

As catalyzing or carryingsalt I may employ any of a large number ofcompounds WlllCl). are capable of acting in the manner explained,particularly ferrous chloride zinc "2 chloride 'or ammonium chloride.

may define "the term carrying salt "as any salt capable of formingvolatile compounds with tinfl", p

I Thesaidsalt may be employed in comparactively small quantities for"instance 0,-5 per cent tov 5 per cent of the weightot material undertreatment. The collecting metal may be employed in quantities suitableto form alloys of the desired composition with the tin present in thecharge; The most economical and elhcientproportions of bother either unlay' bereadily rfoundfor each material to be; treated calculation and bya few prelimi-:

[nary tests? fiel j l The several methods ofcarryingjoutthis In fact Iinvention as far as the reduction of the tint 1s concerned, may;besubstantially similar to those described in co -pending applicationSerial No. 275,267, filed lWay 4th, 1928, 1

or I may employ carbonaceous or gaseous re: ducmg agents 111 l1eu ofmetal powders, in

.fof tin and nickel so, produced by means of 1 i any'lmown or suitablerecovery process, for

instance magnetic or gravity concentration; -A goodmethod 1s to employgraded nickel powder orusma ll pellets of say minus 50 plus 100- mesh.After treatment" the alloy may then be separated fromthegangue mattering been allpassed through the mesh or, other selected screemprevious totreat ment.;

To illustrate the principles of my inven-. .80

tion I avilldescribe some ojfmy early experi ments wherein- Iemployedzinc chloride as Empermen t No. l

Anore ofllode tin jtaken' froma Cornish a minewas selecte-d carrying 1.2per cent Sn as cas'siterite in a matrix of granite with-a few per centof pyrites. To emphasize the re; sults and-make mere, accuratedeterminations this ore was enriched to 6.93 per cent SH. by theaddition of a Nigerian tin concentrate containing 58.5 per cent asJcassiteritein the gratio of ofconcentrate tog-of Cornish" ore. a r aThe charge-mixture consisted 0545 grams of Cornish ore and 5 grams ofcassiterite with 5 grams iron powder all intimately mixed and ground topass 100 mesh sieve.

W'ith the charge was also intimately mixed 2.0 grams anhydrous zincchloride.

The whole was placed. in a nickel crucible with cover weighing 70.35grams andheated for QOminutes to between 700 and 800 centigrade andallowed to cool without admission of air. The whole had lost barely 2grams in weight. On opening the crucible the charge was found to haveuniformlysln'unk and ,caked to a soft but cohcrentsinter and could beremoved from the crucible in one piece by merelytipping it out andafterwards pulverized with great ease. p p

The charge contained only a trace of tin. The crucible had increased inweight by 3.7 gramsand on assay was found to contain practically thewhole of the tin originally in the ore and concentrate namely, 3.47grams. The crucible was clean and with metallic lustre on inside surfacewhich however was blistered all over. The inner blis tered surfaceassayed as high as 28 per cent Sn and the rest of the crucible inreducing amounts at progressively greater depths from the inner surface.

Experiment N0. 2

of the Cornish ore by the Nigerian cassitera ite. The quantities wereCornish ore 7 5 grams, iron powder 5 grams. Zinc chlorideone pieceplaced in centre ofcharge in this case'2.0 grams, crucible and cover67.8 grams. f

The charge was treated as in No. 1 and after coolingthe ore contained notin" and the crucible-quite clean and of metallic surfacehad increasedby 1.3 grams in weight. This .was found to include the whole of the 0.9gram of tin originally contained in and now taken from the ore and someiron arsenic and sulphur.

The experiment repeated :1 number of times with fresh charges ofore butusing the same crucible resulted in a continualincrease of weight of thecrucible by absorption" of all the tin in each successive fresh chargein under these conditions but not to anything ike thesame extent. Thecharges after treatment usually contained about A; to of the I originaltin content. s

equally good results in each case. They were also repeated usingcharcoal and again using anthracite as reducing agents and again usingiron containers and employing a nickel collecting metal in the form ofgraded small a. previous roast whereby arsenic and sulphur are removedin known ways improves the quality of the alloys of tin and nickelproduced as aforesaid and also. reduces the amounts of reagentsrequired. Some iron usually enters the alloy together withthe tin, theamount depending both on the temperature and period of the heating andon the proportion of the iron present. Such iron is notusuallydetrimental in such alloys and is sometimes of advantage. l

I will state two typical examples of the production of such allo s usingiron chloride and carbonaceous reducing agents in the presence of ironoxide but I do not limit myself to these examples or to the precise formof the reactions orto the materials or the proportions of materialsindicated. These exampics are based on my actual experiments.

' Eaiample N o. 1

It is desired to reduce the tin, oxide in a good grade ore or a lowgrade cassiterite concentrate, putting the tin into alloy with bothnic'kel and iron 50 as to make an alloy which can be separated from thegangue matter magnetically and which shall contain a comparatively smallamount of nickel per unit of tin this being desirable foreconomic-reasons in the subsequent recovery of both metals.

A suitable mixture is approximately as follows I i Pounds Ore (orconcentrate) containing 6 per cent Sn"; 200 FQCI QH O (or anhydrous inproportion); 2 Fe (HO) (or anhydrous in proportion); .i i. 11 Coal (orcharcoal) ti Nickel (added as metal pellets or as metal powder or asoxide or hydrated oxide) as"metal 20 Total chargeu n 239 But mixturesricher. in tin and/or iron and poorer in nickel or vice versa may beemployed if preferred for any reason.

The 'nickel is here indicated as applied in the form of metal in adivided state. It may however be applied as oxide or hydroxide just asit'is precipitated from its solutions or after calcining or reducing toa metal powder, in which case" additional coal or 1 v sey os Jother'rcducing agent may heused" to reduce the oxide to metal. V

After heating to ahOutTOO to, 9000 degrees ce,nti'grade for one hour orless duringwhich time small quantities of H and CO- with CO and a littleHCl will distill oil, all the tin and nickel and most of the ironpresent will be found in association as a highly magnetic alloy ofapproximately the following composition Per cent Ni 51.75 "Fe 16.95 sum;31.3

and the weight approximately 38 lbs. of alloy. V V 1 This alloy may becompletely and easily separated from the gangue by magnetic means.

If the nickel employed is nickel which has een reduced trom its hydratedoxide for instance on farther treatment of the alloy for recovery of itstin) and is converted into tiny pellets of +50 screen size for instanceby the well known Mend nickel carhonyl reaction or otherwise, thesepellets will flOre or concentrate (containing 6 per cent Sn) l 200 oranh drous salts V' :1 "L 1 r 1. 0 actin ascaealyners 0 5 G only nrthiscase. Goaln n; n 3 Nickel pellets or as powder or as OXMlQ or hydroxide)(metal) 20 Total charge 22 a The composition 0 .0 r L Si1 f 'M 3?. O N-ll 0 and the weight approximately 33 has,

It the charge has not been overheated this ing; the charges 4 L i 1 i inan nnown or SLllofiblQ wa OXlClGllEEVQ allheen previously y y that metalstill .in the solid novel and ,hitl'ierto unknown.

I cannot yet offer any definite explanation alloy is also easilyseparated lay-screening or by magnetic means.

* with low iron and low nickel content are somewhat less though stillappreciably maq'netic up to about 65to per cent of e is as follows:

I I a Pounds I t'rate (60% Sn) 200 e; El) oranhydronsl u n i 5FeGhslr-fi) or anhydrous 10 Goal; '30 Nickel (metal) 200 The resultingalloy will weigh andas-say az-s follows V p Percent Gil The temperatureof reduction should'not exceed ina-11y case 800- to 900 degrees centigrade and air should he'excluded whilst heat-- After the tin has beencollected'into the collectingtmetal 1 may recover it therefrom Or I maymelt the alloys. andcastthem into anodes-and use suclraned'e s in anelectrolytic bath of suitable composition whereby I may obtain-tin andnickel plated out separately onto sheet metal cathodes in known or suitable ways whilst the anodesare dissolved and serve to depolorize thebaths so that a' minimlun otelectric energy is required therefor andthebaths are refurnished by the solntioni' of metals at the anodes. I

i Ars'tar lam aware the reaction herein {er itself from a, distancethrough aconsidera'hle thickness of charge intoia collect ing metalwithout contact therewith and with phase are all of the precisemeehanisinof these reactions which require further study, but in generalit may he conceived that tin in the formof tin chloride isvapourized insmallamounts and that the catalyzing or carrying salt also i in the formof a vapour bath of a very hig degree of mobility transfers thetin-chloride vapour rapidly into contact with the exposed surfaces ofthe collecting metal whlch in turn at the temperatures employeddecomposes it 1' anda-hsorbs the tin like a sponge Whilst.

chlorineset freeandcomhines With addisemi metal in the charge. It isprobable before described whereby they tinv will tran s- 1110 di ategrade ores or products and in the case of tin bearing slags and ofcomplex tin bearing ores containing other metals and sulphur, the 'tinmay be recovered at only a fraction of the cost of existing methods andmany such materials now of no commercial value may by its use beprofitably employed for the production of tin.

Throughout this specification the terms ore or material are intendedwhenever applicab e by the context to include any ore, con- I centrate',product, slag, residue or other material from which tin is to beextracted. The terms furnace or retort are intended to includehorizontal. sloping or vertical retorts; muflie or open furnaces, withor without nibbling devices: revolving furnaces, kilns, tunnel ovens,pallet chains of Dwight Lloyds sintering type; or any form of heatingap- Daratus the heat for which may be supplied by solid, liquid tricity.

What I claim is;

1. In the extraction of tin from a mass of tin-bearing material, mixingwith the mass a carrying salt and a collecting metal. and heating themass to cause the tin to alloy with the collecting metal.

' 2. In the extraction of tin from amass of tin-hearing material,reducing the tin to metallic form, mixin p," with the mass a carryingsalt and a collecting metal after reduction has con'uncnccd, heating themassto cause the tin to alloy with the collecting,

metal, and subsequently separating the tin from said collecting metal. i3. In the extraction of the tin from a mass of tin-bea ring material,mixing with the mass 21 metal chloride and a collecting metal, andheating the mass to cause the tin to alloy with the collecting metal.

4. In the extraction of tin from a mass of tin-bearing material. mixingwith the mass a or gaseous fuel or by elec-;

EDGAR ARTHUR ASHCROFT.

